There is a growing desire to use point to multi-point services in wireless communication systems. As shown in FIG. 1 in point to multi-point (PtM), one service is sent from a single point, such as a base station 10, to multiple points, such as multiple user equipments 121-123. Examples of point to multi-point services are multimedia broadcasts and multicast services.
In the third generation partnership program (3GPP) proposed system, one proposed channel that could be used for such services is the forward access channel (FACH). The FACH is a downlink common transport channel (TrCH) that can be received by all users. The FACH TrCH is broadcast by applying it to the secondary common control physical channel (S-CCPCH). The S-CCPCH is transmitted to all the cell users.
To limit the radio recourses utilized by the S-CCPCH, the S-CCPCH data rate is limited. To illustrate, if a high data rate service was transmitted over the S-CCPCH, it would need to be transmitted using a low data redundancy to achieve that high data rate. Since the S-CCPCH is transmitted to the entire cell, it is transmitted at a power level sufficient for reception by a user at the periphery of the cell at a certain quality of service (QOS). Broadcasting a high data rate service at this power level would increase interference to other users reducing the capacity of system, which is extremely undesirable, due to the inefficient use of cell resources.
Additionally, due to the broadcast nature of the S-CCPCH and FACH, the radio resources required for the S-CCPCH and FACH are rather static, due to channel allocation and messaging on these channels being provided at a relatively slow rate by layer 3 signaling techniques. The modulation and coding set (MCS) and transmission power level used by the S-CCPCH needs to be sufficient to maintain a certain QOS at the periphery of the cell. The static nature of the S-CCPCH configuration does not allow dynamic adjustment of these parameters to make efficient use of radio resources. Additionally, scheduling of transmissions also occur at this slow rate, which does not allow for efficient use of this radio resource and does not allow for efficient multiplexing of data streams to each user.
Another channel that can be used for point to point (PtP) services is the downlink shared channels (DSCHs). The DSCHs are shared by multiple users. Transmissions to different users (user equipments) over the DSCH are separated by time. As a result, the DSCHs are time shared channels.
Each user using the DSCH has an uplink and a downlink dedicated control channel. These control channels allow a more efficient radio resource utilization of the DSCHs. These control channels allow for power control for each user's transmission over the DSCH and also allow for beam forming to better separate user transmissions. The DSCH's use of power control and beam forming allows for better resource utilization than provided by FACH channels.
To receive information over the DSCH, a user first monitors its dedicated downlink control channel. A burst in the downlink control channel may have both a first portion and a second portion of a transport format combination indicator (TFCI). The first portion indicates the transport format of the downlink dedicated channel. The second portion indicates existence and the transport format of a subsequent DSCH transmission. If a DSCH transmission to the user is going to be sent to the user, the downlink control channel has the second portion of the TFCI set. The transmission will occur in a subsequent transmission time interval (TTI), after a specified time period. The user then monitors the DSCH for its transmission. To verify that the user is the correct recipient of the DSCH transmission, it checks the transmission for its user identifier. If a transmission is not going to be sent, the second portion of the TFCI is not present on the downlink dedicated control channel.
Although the DSCHs allows for a more efficient utilization of radio resources, only point to point services can be handled. To handle multiple reception points, multiple transmissions are made over the DSCH. Accordingly, transmission to many users requires many transmissions over the DSCH, using valuable radio resources.
Accordingly, it is desirable to have added flexibility in providing wireless point to multi-point services.